Method of removing coatings from conductors



Sept. 3, 1929. H. P. HOLLNAGEL METHOD OF REMOVING COATINGS FROMCONDUCTCRS Invehtor Hevberc F. Hol lnagel,

Filed April 11, 1924 b4 44.x, HIS Attovney.

Patented Sept. 3,1929.

1,726,623- PATENT OFFICE.

UNITED STATES HERBERT P. HOLLNAGEL, F 'SWAMISCOTT, MASSACHUSETTS,ASSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METHOD OF REMOVING COATINGS FROM CONDUCTORS.

Application filed April 11, 1984. Serial No. 705,786.

The present invention relates to the removal from electrical conductorsof sheaths or coatings of insulating materials of various kinds, as forexample cotton, silk, paper,

asphalt, varnishes, asbestos, or the like, which may be present eitheralone or in combination. It may be necessary to remove these coatingseither locally to make electric connections or over a long length of 1wire when, for example, the insulation has been damaged, or insulatedwire has been rejected for one reason or another.

Heretofore, these various insulating coatings have been removedmechanically, for

example, by scraping, but this method is time consuming, even for theremoval of short lengths of insulation.

In accordance with my invention; the in sulation is removed moreconveniently and expeditiously by a chemically active agent, preferablya fused alkali. The wire is not only freed from insulation by thismethod but also is annealed and has its surface cleaned, therebyfacilitating subsequent operations. In accordance with another featureof my invention, the uncoated conductor is subjected after thistreatment, while chemically clean, to a surface alloyage with anothermetal to facilitate making electric connections. Other features of myinvention will be set forth hereinafter and pointed out in theaccompanying claims.

The accompanying drawing shows in Fig.

1 a somewhat diagrammatic vertical section of an apparatus for removinginsulation from wire in continuous lengths and Fig.

2 shows in vertical section two heated receptacles respectivelycontaining a medium for removing insulation from the ends of insulatedwire and a fused metal for surface alloying the Wire, preparatory tomaking connections. I

My invention is applicable for the rapid removal of various kinds ofinsulation, the more common example being cellulose compositions, suchas paper or cotton and gummy organic compositions, such as, variouskinds of gums, asphalts, varnishes, lacquers, and synthetic resins.Insulation consisting of complex silicates, such as asbestos can beremoved in the same way. Non-vitreous enamels, that is coatings ofoxidized or polymerized oil, are removed with ease.

I will first explain the removal of insulation from continuous lengthsof wire. Ex-

peditious removal of insulation will ermit the salvaging of wire uponwhich t e insulation has been damaged. Fig. 1 shows such a wire 2unwinding from a reel 3 pass ing through the treating apparatus andfinally being wound upon a receiving reel 4, the entire apparatus beingsupported upon a table 5. The decoating bath is contained within anelongated tank 7 consisting of iron or the like. The decoatingcomposition consists of fused lye, which has been carefully freed fromwater. Chemical purity is not essential.

I may use commercial lye which consists of about 94% of sodium hydrate,about 2% of sodium carbonate, about 2% of sodium chloride and about 2%sodium sulphate. Potash lye, and alkali sulphite can be used. A- secondtank 8 contains water or other washing medium. An auxiliary abrasionmechanism, which will be described presently, is used in some cases.

The alkali bath 6 is heated to a fusing I temperature, or somewhathigher, by any convenient means, as for example, an electric heater 10.The temperature preferably should not exceed 700 C. A vent pipe 11provides for the removal of fumes. The wire 2 is carried over suitableguides 12, 13, 14 through a discharge neck 15 into the washing tank,where it is received vby guides l6, 17. A felt Washer, or similar wipingdevice preferably is interposed between the 1 guides as indicated. Aflow of water should be maintained through the tank through inlet andoutlet pipes (not shown). As some times small patches of tenaceousinsulation may adhere loosely to the wire after the chemical treatment,rotating brushes 18, 19,

are provided between which the wire is passed as an extra precaution,but these brushing devices are not always necessary. The necessarypullor tension to carry the wire through the described apparatus is ap pliedby ,a reel 20, which is driven by a motor 21. Power also is derived fromthis motor to drive the brushes 18, 19.

As small diameter wires tend to become reduced in cross-section by thestretching effect of the tension under which they areput, they arepreferably drawn through a die as indicated at 22, to bring thecross-section of the wire to a standard size. The wire becomes softened,by the stripping process, that is, by contact with the heated bath oflye and the subsequent washing treatment. The drawing through a diesomewhat rehardens or tempers the wire to a state approximating itsoriginal condition.

Various speeds and temperatures may be used ,according to theconditions. As an illustrative example, 81 mil copper wire insulatedwith an inner coat of a vegetable oil enamel and externally by a doublecoating of cotton, can be stripped by feeding through the fused bath at8 feet per minute at a temperature of about 620 C. The imiron, or othersuitable material, is provided with an electrical heater 26. A heatinsulatin jacket 27 surrounds the container. A shield 28 preferably isprovided above the bath to prevent spattering of the hydroxide. An airblast supplied by a pipe 29 and being directed across the surface of thebath, is highly desirable to prevent charring and burning of thecombustible insulations. In Order to prevent unravelling of fibreinsulated wires, the cotton, silk, or other fibre first is impregnatedover a region. overlapping the section to be stripped with shellac andbaked at 100 C. for about 30 minutes. The molten hydroxide removes theimpregnated insulation leaving a clear margin of shellac-coated coveringwhich will not unravel. In some cases it is desirable to first treat thecotton or the like with parafline.

The immersion of the ends should occur gradually to reduce foaming andthe hydroxide should act for a length of time varying from a few secondsto about ten seconds until the insulation is removed. The wires then areheld in" a spray of water to wash out a residue of hydroxide and finallyare dried. When it is desirable to tin the bared ends of the conductors,to facilitate soldering or for any other reason they are immediatelydipped, without washing, into molten solder, preferably through a thinlayer of molten hydroxide. Fig. 2 shows a pot 30, also electricallyheated by a heater 31, and containing a quantity 32 of alloying metal,

such as solder and a superimposed layer 33 of sodium hydroxide, or othersuitable flux. As indicated, the leads of the coil 34 are dipped intothis bath to tin the conductors.

While I have described specific embodiments of myinvention, I do notwish to be limited to the particular form shown and described as it willbe apparent that many modifications therein may be made withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The method of removing coatings of cellulose fibres from metalobjects which consists in bringing fused caustic alkali into contactwith said coating, and thereu on washing with water to remove excess a1ali and reaction products. a

2. The method of removing organic insulating coatings from conductorswhich consists in passing said conductors through fused alkali andthereupon washing with water.

'3. The method of removing fibrous insulating coatings from the endsofelectrical conductors by chemical decomposition, which consists inapplying shellac to the coating over a region within which the boundaryof decomposition will occur, heat hardening'the shellac, treatinguncoated material adjacent said boundary by a caustic alkali, andWashing with water.

4. The method of removing cellulose insulation from an electricconductor which consists in immersin the portion of said con doctor tobe freed from such insulation in fused caustic alkali at a temperaturein excess of about 400 C. and thereupon washing with water to removeexcess of alkali and decomposition products.

5. The method ofremoving organic insulation from metal conductors whichconsists in bringing said conductors into contact with a fused reagentcontaining a commercial lye and thereafter removing reaction productswith water.

6. The method of removing organic insulation from metal conductors whichconsists in bringing said conductors into contact with a fused reagentcontaining a substantial proportion of strong alkali and thereafterremoving reaction products with water.

In witness whereof, I have hereunto set my hand this eighth day ofApril, 1924.

HERBERT- P. HOLLNAGEL.

